Method for controlling transmission power of sounding reference signal in wireless communication system and apparatus for same

ABSTRACT

Disclosed in the present application is a method for transmitting a sounding reference signal (SRS) from a terminal to a base station in a time division duplex (TDD) system. More specifically, the method comprises: a step of establishing a first subframe set and a second subframe set through an upper layer, and step of transmitting the sounding reference signal from a specific subframe to the base station, wherein the first subframe set and the second subframe set are configured by an uplink subframe and/or a special subframe, each of the first subframe and the second subframe is associated with a power control process for transmitting an uplink data channel, and wherein the transmission power of the sounding reference signal is determined on the basis of a specific power control process associated with a subframe set to which the specific subframe belongs, from among the first subframe set and the second subframe set.

This application is a 35 USC §371 National Stage entry of InternationalApplication No. PCT/KR2014/005515 filed on Jun. 23, 2014, and claimspriority to U.S. Provisional Application Nos. 61/838,849 filed on Jun.24, 2013; 61/842,369 filed on Jul. 2, 2013; 61/894,396 filed on Oct. 22,2013; 61/897,210 filed on Oct. 29, 2013 and 61/931,559 filed on Jan. 24,2014, all of which are hereby incorporated by reference in theirentireties as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more specifically, to a method for controlling transmission power of asounding reference signal in a wireless communication system and anapparatus for the same.

BACKGROUND ART

3GPP LTE (3rd generation partnership project long term evolutionhereinafter abbreviated LTE) communication system is schematicallyexplained as an example of a wireless communication system to which thepresent invention is applicable.

FIG. 1 is a schematic diagram of E-UMTS network structure as one exampleof a wireless communication system. E-UMTS (evolved universal mobiletelecommunications system) is a system evolved from a conventional UMTS(universal mobile telecommunications system). Currently, basicstandardization works for the E-UMTS are in progress by 3GPP. E-UMTS iscalled LTE system in general. Detailed contents for the technicalspecifications of UMTS and E-UMTS refers to release 7 and release 8 of“3rd generation partnership project; technical specification group radioaccess network”, respectively.

Referring to FIG. 1, E-UMTS includes a user equipment (UE), an eNode B(eNB), and an access gateway (hereinafter abbreviated AG) connected toan external network in a manner of being situated at the end of anetwork (E-UTRAN). The eNode B may be able to simultaneously transmitmulti data streams for a broadcast service, a multicast service and/or aunicast service.

One eNode B contains at least one cell. The cell provides a downlinktransmission service or an uplink transmission service to a plurality ofuser equipments by being set to one of 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz,15 MHz, and 20 MHz of bandwidths. Different cells can be configured toprovide corresponding bandwidths, respectively. An eNode B controls datatransmissions/receptions to/from a plurality of the user equipments. Fora downlink (hereinafter abbreviated DL) data, the eNode B informs acorresponding user equipment of time/frequency region on which data istransmitted, coding, data size, HARQ (hybrid automatic repeat andrequest) related information and the like by transmitting DL schedulinginformation. And, for an uplink (hereinafter abbreviated UL) data, theeNode B informs a corresponding user equipment of time/frequency regionusable by the corresponding user equipment, coding, data size,HARQ-related information and the like by transmitting UL schedulinginformation to the corresponding user equipment. Interfaces foruser-traffic transmission or control traffic transmission may be usedbetween eNode Bs. A core network (CN) consists of an AG (access gateway)and a network node for user registration of a user equipment and thelike. The AG manages a mobility of the user equipment by a unit of TA(tracking area) consisting of a plurality of cells.

Wireless communication technologies have been developed up to LTE basedon WCDMA. Yet, the ongoing demands and expectations of users and serviceproviders are consistently increasing. Moreover, since different kindsof radio access technologies are continuously developed, a newtechnological evolution is required to have a future competitiveness.Cost reduction per bit, service availability increase, flexiblefrequency band use, simple structure/open interface and reasonablepower.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method for controlling transmission power of a sounding referencesignal in a wireless communication system and an apparatus for the same.

Technical Solution

In an aspect of the present invention, a method for transmitting, by aUE, a sounding reference signal (SRS) to a base station in a timedivision duplex (TDD) system includes: configuring a first subframe setand a second subframe set through a higher layer; and transmitting thesounding reference signal to the base station through a specificsubframe, wherein the first subframe set and the second subframe set areconfigured by at least one of an uplink subframe and a special subframe,wherein each of the first subframe and the second subframe is associatedwith a power control process for uplink data channel transmission,wherein transmission power of the sounding reference signal isdetermined on the basis of a predetermined power control processassociated with a subframe set to which the specific subframe belongs,from among the first subframe set and the second subframe set.

In another aspect of the present invention, a method for receiving, by abase station, a sounding reference signal (SRS) from a UE in a TDDsystem includes: configuring a first subframe set and a second subframeset through a higher layer; and receiving the sounding reference signalfrom the UE through a specific subframe, wherein the first subframe setand the second subframe set are configured by at least one of an uplinksubframe and a special subframe, wherein each of the first subframe andthe second subframe is associated with a power control process foruplink data channel transmission, wherein transmission power of thesounding reference signal is determined on the basis of a predeterminedpower control process associated with a subframe set to which thespecific subframe belongs, from among the first subframe set and thesecond subframe set.

The transmission power of the sounding reference signal may bedetermined using one or more parameters defined in the predeterminedpower control process.

The first subframe set may include a subframe fixed as an uplinksubframe and the special frame only. An uplink subframe included in thesecond subframe set may be a subframe changeable to a downlink subframeaccording to instruction of the base station.

The special subframe may include a region for uplink transmission, andonly the sounding reference signal may be transmitted in the region foruplink transmission.

Transmission power of a sounding reference signal transmitted in a firstspecial subframe and transmission power of a sounding reference signaltransmitted in a second special subframe may be independentlydetermined.

Advantageous Effects

According to embodiments of the present invention, a terminal canefficiently control transmission power of a sounding reference signal ina wireless communication system.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an E-UMTS network structure as oneexample of a wireless communication system.

FIGS. 2(a) and 2(b) are diagrams of structures of control and userplanes of radio interface protocol between a 3GPP radio access networkstandard-based user equipment and E-UTRAN.

FIG. 3 is a diagram for explaining physical channels used for 3GPPsystem and a general signal transmission method using the physicalchannels.

FIG. 4 is a diagram of a structure of a downlink radio frame in an LTEsystem.

FIG. 5 is a diagram for a structure of an uplink radio frame in an LTEsystem.

FIG. 6 illustrates a structure of a radio frame in an LTE TDD system.

FIG. 7 is a view illustrating a concept of a carrier aggregation scheme.

FIG. 8 illustrates an example of dividing one radio frame into subframeset #1 and subframe set #2.

FIG. 9 illustrates a method of determining the number of symbols towhich a PUSCH is mapped.

FIG. 10 is a block diagram for an example of a communication deviceaccording to one embodiment of the present invention.

BEST MODE

In the following description, compositions of the present invention,effects and other characteristics of the present invention can be easilyunderstood by the embodiments of the present invention explained withreference to the accompanying drawings. Embodiments explained in thefollowing description are examples of the technological features of thepresent invention applied to 3GPP system.

In this specification, the embodiments of the present invention areexplained using an LTE system and an LTE-A system, which is exemplaryonly. The embodiments of the present invention are applicable to variouscommunication systems corresponding to the above mentioned definition.In particular, although the embodiments of the present invention aredescribed in the present specification on the basis of FDD, this isexemplary only. The embodiments of the present invention may be easilymodified and applied to H-FDD or TDD. And, in the present specification,a base station can be named by such a comprehensive terminology as anRRH (remote radio head), an eNB, a TP (transmission point), an RP(reception point), a relay and the like.

FIG. 2 is a diagram for structures of control and user planes of radiointerface protocol between a 3GPP radio access network standard-baseduser equipment and E-UTRAN. The control plane means a path on whichcontrol messages used by a user equipment (UE) and a network to manage acall are transmitted. The user plane means a path on which such a datagenerated in an application layer as audio data, internet packet data,and the like are transmitted.

A physical layer, which is a 1st layer, provides higher layers with aninformation transfer service using a physical channel. The physicallayer is connected to a medium access control layer situated above via atransport channel (trans antenna port channel). Data moves between themedium access control layer and the physical layer on the transportchannel. Data moves between a physical layer of a transmitting side anda physical layer of a receiving side on the physical channel. Thephysical channel utilizes time and frequency as radio resources.Specifically, the physical layer is modulated by OFDMA (orthogonalfrequency division multiple access) scheme in DL and the physical layeris modulated by SC-FDMA (single carrier frequency division multipleaccess) scheme in UL.

Medium access control (hereinafter abbreviated MAC) layer of a 2nd layerprovides a service to a radio link control (hereinafter abbreviated RLC)layer, which is a higher layer, on a logical channel. The RLC layer ofthe 2nd layer supports a reliable data transmission. The function of theRLC layer may be implemented by a function block within the MAC. PDCP(packet data convergence protocol) layer of the 2nd layer performs aheader compression function to reduce unnecessary control information,thereby efficiently transmitting such IP packets as IPv4 packets andIPv6 packets in a narrow band of a radio interface.

Radio resource control (hereinafter abbreviated RRC) layer situated inthe lowest location of a 3rd layer is defined on a control plane only.The RRC layer is responsible for control of logical channels, transportchannels and physical channels in association with a configuration, are-configuration and a release of radio bearers (hereinafter abbreviatedRBs). The RB indicates a service provided by the 2nd layer for a datadelivery between the user equipment and the network. To this end, theRRC layer of the user equipment and the RRC layer of the networkexchange a RRC message with each other. In case that there is an RRCconnection (RRC connected) between the user equipment and the RRC layerof the network, the user equipment lies in the state of RRC connected(connected mode). Otherwise, the user equipment lies in the state of RRCidle (idle mode). A non-access stratum (NAS) layer situated at the topof the RRC layer performs such a function as a session management, amobility management and the like.

A single cell consisting of an eNode B (eNB) is set to one of 1.25 MHz,2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz of bandwidths and thenprovides a downlink or uplink transmission service to a plurality ofuser equipments. Different cells can be configured to providecorresponding bandwidths, respectively.

DL transport channels for transmitting data from a network to a userequipment include a BCH (broadcast channel) for transmitting a systeminformation, a PCH (paging channel) for transmitting a paging message, adownlink SCH (shared channel) for transmitting a user traffic or acontrol message and the like. DL multicast/ broadcast service traffic ora control message may be transmitted on the DL SCH or a separate DL MCH(multicast channel). Meanwhile, UL transport channels for transmittingdata from a user equipment to a network include a RACH (random accesschannel) for transmitting an initial control message, an uplink SCH(shared channel) for transmitting a user traffic or a control message. Alogical channel, which is situated above a transport channel and mappedto the transport channel, includes a BCCH (broadcast channel), a PCCH(paging control channel), a CCCH (common control channel), a MCCH(multicast control channel), a MTCH (multicast traffic channel) and thelike.

FIG. 3 is a diagram for explaining physical channels used for 3GPPsystem and a general signal transmission method using the physicalchannels.

If a power of a user equipment is turned on or the user equipment entersa new cell, the user equipment may perform an initial cell search jobfor matching synchronization with an eNode B and the like [S301]. Tothis end, the user equipment may receive a primary synchronizationchannel (P-SCH) and a secondary synchronization channel (S-SCH) from theeNode B, may be synchronized with the eNode B and may then obtaininformation such as a cell ID and the like. Subsequently, the userequipment may receive a physical broadcast channel from the eNode B andmay be then able to obtain intra-cell broadcast information. Meanwhile,the user equipment may receive a downlink reference signal (DL RS) inthe initial cell search step and may be then able to check a DL channelstate.

Having completed the initial cell search, the user equipment may receivea physical downlink shared control channel (PDSCH) according to aphysical downlink control channel (PDCCH) and an information carried onthe physical downlink control channel (PDCCH). The user equipment may bethen able to obtain a detailed system information [S302].

Meanwhile, if a user equipment initially accesses an eNode B or does nothave a radio resource for transmitting a signal, the user equipment maybe able to perform a random access procedure to complete the access tothe eNode B [S303 to S306]. To this end, the user equipment may transmita specific sequence as a preamble on a physical random access channel(PRACH) [S303/S305] and may be then able to receive a response messageon PDCCH and the corresponding PDSCH in response to the preamble[S304/S306]. In case of a contention based random access procedure(RACH), it may be able to additionally perform a contention resolutionprocedure.

Having performed the above mentioned procedures, the user equipment maybe able to perform a PDCCH/PDSCH reception [S307] and a PUSCH/PUCCH(physical uplink shared channel/physical uplink control channel)transmission [S308] as a general uplink/downlink signal transmissionprocedure. In particular, the user equipment receives a DCI (downlinkcontrol information) on the PDCCH. In this case, the DCI contains such acontrol information as an information on resource allocation to the userequipment. The format of the DCI varies in accordance with its purpose.

Meanwhile, control information transmitted to an eNode B from a userequipment via UL or the control information received by the userequipment from the eNode B includes downlink/uplink ACK/NACK signals,CQI (Channel Quality Indicator), PMI (Precoding Matrix Index), RI (RankIndicator) and the like. In case of 3GPP LTE system, the user equipmentmay be able to transmit the aforementioned control information such asCQI/PMI/RI and the like on PUSCH and/or PUCCH.

FIG. 4 is a diagram for showing an example of a control channel includedin a control region of a single subframe in a DL radio frame.

Referring to FIG. 4, a subframe consists of 14 OFDM symbols. Accordingto a subframe configuration, the first 1 to 3 OFDM symbols are used fora control region and the other 13˜11 OFDM symbols are used for a dataregion. In the diagram, R1 to R4 may indicate a reference signal(hereinafter abbreviated RS) or a pilot signal for an antenna 0 to 3.The RS is fixed as a constant pattern in the subframe irrespective ofthe control region and the data region. The control channel is assignedto a resource to which the RS is not assigned in the control region anda traffic channel is also assigned to a resource to which the RS is notassigned in the data region. The control channel assigned to the controlregion may include a physical control format indicator channel (PCFICH),a physical hybrid-ARQ indicator channel (PHICH), a physical downlinkcontrol channel (PDCCH), and the like.

The PCFICH (physical control format indicator channel) informs a userequipment of the number of OFDM symbols used for the PDCCH on everysubframe. The PCFICH is situated at the first OFDM symbol and isconfigured prior to the PHICH and the PDCCH. The PCFICH consists of 4resource element groups (REG) and each of the REGs is distributed in thecontrol region based on a cell ID (cell identity). One REG consists of 4resource elements (RE). The RE may indicate a minimum physical resourcedefined as ‘one subcarrier×one OFDM symbol’. The value of the PCFICH mayindicate the value of 1 to 3 or 2 to 4 according to a bandwidth and ismodulated into a QPSK (quadrature phase shift keying).

The PHICH (physical HARQ (hybrid-automatic repeat and request) indicatorchannel) is used for carrying HARQ ACK/NACK for an UL transmission. Inparticular, the PHICH indicates a channel to which DL ACK/NACKinformation is transmitted for UL HARQ. The PHICH consists of a singleREG and is scrambled cell-specifically. The ACK/NACK is indicated by 1bit and modulated into BPSK (binary phase shift keying). The modulatedACK/NACK is spread into a spread factor (SF) 2 or 4. A plurality ofPHICHs, which are mapped to a same resource, composes a PHICH group. Thenumber of PHICH, which is multiplexed by the PHICH group, is determinedaccording to the number of spreading code. The PHICH (group) is repeatedthree times to obtain diversity gain in a frequency domain and/or a timedomain.

The PDCCH (physical DL control channel) is assigned to the first n OFDMsymbol of a subframe. In this case, the n is an integer more than 1 andindicated by the PCFICH. The PDCCH consists of at least one CCE. ThePDCCH informs each of user equipments or a user equipment group of aninformation on a resource assignment of PCH (paging channel) and DL-SCH(downlink-shared channel), which are transmission channels, an uplinkscheduling grant, HARQ information and the like. The PCH (pagingchannel) and the DL-SCH (downlink-shared channel) are transmitted on thePDSCH. Hence, an eNode B and the user equipment transmit and receivedata via the PDSCH in general except a specific control information or aspecific service data.

Information on a user equipment (one or a plurality of user equipments)receiving data of PDSCH, a method of receiving and decoding the PDSCHdata performed by the user equipment, and the like is transmitted in amanner of being included in the PDCCH. For instance, assume that aspecific PDCCH is CRC masked with an RNTI (radio network temporaryidentity) called “A” and an information on data transmitted using aradio resource (e.g., frequency position) called “B” and a DCI formati.e., a transmission form information (e.g., a transport block size, amodulation scheme, coding information, and the like) called “C” istransmitted via a specific subframe. In this case, the user equipment ina cell monitors the PDCCH using the RNTI information of its own, ifthere exist at least one or more user equipments having the “A” RNTI,the user equipments receive the PDCCH and the PDSCH, which is indicatedby the “B” and the “C”, via the received information on the PDCCH.

FIG. 5 is a diagram for a structure of an uplink subframe used in LTEsystem.

Referring to FIG. 5, an UL subframe can be divided into a region towhich a physical uplink control channel (PUCCH) carrying controlinformation is assigned and a region to which a physical uplink sharedchannel (PUSCH) carrying a user data is assigned. A middle part of thesubframe is assigned to the PUSCH and both sides of a data region areassigned to the PUCCH in a frequency domain. The control informationtransmitted on the PUCCH includes an ACK/NACK used for HARQ, a CQI(channel quality indicator) indicating a DL channel status, an RI (rankindicator) for MIMO, an SR (scheduling request) corresponding to an ULresource allocation request, and the like. The PUCCH for a single UEuses one resource block, which occupies a frequency different from eachother in each slot within a subframe. In particular, 2 resource blocksassigned to the PUCCH are frequency hopped on a slot boundary. Inparticular, FIG. 5 shows an example that the PUCCHs satisfyingconditions (e.g., m=0, 1, 2, 3) are assigned to a subframe.

A time within one subframe, in which a sounding reference signal can betransmitted, corresponds to the last symbol in the time domain in thesubframe, and the sounding reference signal is transmitted through adata transmission band in the frequency domain. Sounding referencesignals of multiple UEs, which are transmitted through the last symbolof the same subframe, can be discriminated according to frequencypositions.

FIG. 6 illustrates a structure of a radio frame in an LTE TDD system. Inthe LTE TDD system, a radio frame includes two half frames, and eachhalf frame includes four normal subframes each including two slots, anda special subframe including a downlink pilot time slot (DwPTS), a guardperiod (GP), and an uplink pilot time slot (UpPTS).

In the special subframe, the DwPTS is used for initial cell search,synchronization, or channel estimation in a UE. The UpPTS is used forchannel estimation in an eNB and uplink transmission synchronization ofa UE. That is, the DwPTS is used for downlink transmission and the UpPTSis used for uplink transmission. In particular, the UpPTS is used fortransmission of a PRACH preamble or SRS. In addition, the GP is a periodfor removing interference generated in uplink due to multipath delay ofa downlink signal between uplink and downlink.

Meanwhile, in an LTE TDD system, a UL/DL configuration is shown in Table1 below.

TABLE 1 Uplink- Downlink- downlink to-Uplink Config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In [Table 1] above, D, U, and S refer to a downlink subframe, an uplinksubframe, and the special subframe. In addition, [Table 1] also showsdownlink-to-uplink switch-point periodicity in an uplink/downlinksubframe configuration in each system.

Hereinafter, a carrier aggregation scheme will be described. FIG. 7 is aview illustrating concept of a carrier aggregation scheme.

The carrier aggregation refers to a method of using a plurality offrequency blocks or (logical) cells including uplink resources (orcomponent carriers) and/or downlink resources (or component carriers) bya UE as one large logical frequency band in order to use a widerfrequency band by a wireless communication system. Hereinafter, forconvenience of description, the term ‘component carrier’ willconsistently used.

Referring to FIG. 7, a system bandwidth (system BW) has a maximum of 100MHz as a logical bandwidth. The system BW includes five componentcarriers. Each component carrier has a maximum of 20 MHz of bandwidth. Acomponent carrier includes one or more physically consecutivesubcarriers. Although FIG. 7 illustrates the case in which componentcarriers have the same bandwidth, the case is purely exemplary, andthus, the component carriers may have different bandwidths. In addition,although FIG. 7 illustrates the case in which the component carriers areadjacent to each other in the frequency domain, FIG. 7 are logicallyillustrated, and thus, the component carriers may be physically adjacentto each other or may be spaced apart from each other.

Component carriers can use different center frequencies or use onecommon center frequency with respect to physically adjacent componentcarriers. For example, in FIG. 8, assuming all component carriers arephysically adjacent to each other, center frequency A may be used. Inaddition, assuming that component carriers are not physically adjacentto each other, center frequency A, center frequency B, etc. may be usedwith respect to the respective component carriers.

Throughout this specification, a component carrier may correspond to asystem band of a legacy system. The component carrier is defined basedon a legacy system, and thus, it can be easy to provide backwardcompatibility and to design the system in a wireless communicationenvironment in which an evolved UE and a legacy UE coexist. For example,when an LTE-A system supports carrier aggregation, each componentcarrier may corresponds to a system band of an LTE system. In this case,the component carrier may have any one of bandwidths of 1.25, 2.5, 5,10, and 20 Mhz.

When a system band is extended via carrier aggregation, a frequency bandused for communication with each UE is defined in a component carrierunit. UE A may use 100 MHz as a system band and perform communicationusing all five component carriers. UEs B₁ to B₅ can use only a bandwidthof 20 MHz and perform communication using one component carrier. UEs C₁and C₂ can use a bandwidth of 40 MHz and communication using twocomponent carries. The two component carriers may or may not belogically/physically adjacent to each other. UE C₁ refers to the case inwhich two component carriers that are not adjacent to each other areused and UE C₂ refers to the case in which two adjacent componentcarriers are used.

An LTE system may use one downlink component carrier and one uplinkcomponent carrier, whereas an LTE-A system may use a plurality ofcomponent carriers as illustrated in FIG. 6. In this case, a method forscheduling a data channel by a control channel may be classified into alinked carrier scheduling method and a cross carrier scheduling method.

In more detail, in the linked carrier scheduling method, a controlchannel transmitted through a specific component carrier schedules onlya data channel through the specific component carrier like in a legacyLTE system using a single component carrier.

Meanwhile, in the cross carrier scheduling method, a control channeltransmitted through a primary component carrier (primary CC) using acarrier indicator field (CIF) schedules a data channel transmittedthrough the primary CC or other CC, that is, a secondary CC.

A description will be given of a method for controlling uplinktransmission power in an LTE system.

A method for controlling, by a UE, uplink transmission power thereofincludes open loop power control (OLPC) and closed loop power control(CLPC). The former controls power in such a manner that attenuation of adownlink signal from a base station of a cell to which a UE belongs isestimated and compensated for. OLPC controls uplink power by increasinguplink transmission power when downlink signal attenuation increases asa distance between the UE and the base station increases. The lattercontrols uplink power in such a manner that the base station directlytransmits information (i.e. a control signal) necessary to controluplink transmission power.

The following equation 1 is used to determine transmission power of a UEwhen a serving cell c transmits only a PUSCH instead of simultaneouslytransmitting the PUSCH and a PUCCH in a subframe corresponding to asubframe index i in a system that supports carrier aggregation.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min{\begin{Bmatrix}{{{P_{{CMAX},c}(i)},}\mspace{610mu}} \\{{10{\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{O_{—}{PUSCH}},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

The following equation 2 is used to determine PUSCH transmission powerwhen the serving cell c simultaneously transmits the PUCCH and the PUSCHin the subframe corresponding to the subframe index i in a systemsupporting carrier aggregation.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min{\begin{Bmatrix}{{{10{\log_{10}\left( {{{\hat{P}}_{{CMAX},c}(i)} - {{\hat{P}}_{PUCCH}(i)}} \right)}},}\mspace{374mu}} \\{{10{\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{O_{—}{PUSCH}},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Parameters, which will be described in association with Equations 1 and2, determine uplink transmission power of a UE in the serving cell C.Here, P_(CMAX,c)(i) in Equation 1 indicates maximum transmittable powerof the UE in the subframe corresponding to the subframe index i and{circumflex over (P)}_(CMAX,c)(i) in Equation 2 indicates a linear valueof P_(CMAX,c)(i). {circumflex over (P)}_(PUCCH)(i) in Equation 2indicates a linear value of P_(PUCCH)(i) (P_(PUCCH)(i) indicating PUCCHtransmission power in the subframe corresponding to subframe index i).

In Equation 1, M_(PUSCH,c)(i) is a parameter indicating a PUSCH resourceallocation bandwidth, which is represented as the number of resourceblocks valid for the subframe index i, and is allocated by a basestation. P_(O) _(_) _(PUSCH,c)(j) is a parameter corresponding to thesum of a cell-specific nominal component P_(O) _(_) _(NOMINAL) _(_)_(PUSCH,c)(j) provided by a higher layer and a UE-specific componentP_(O) _(_) _(UE) _(_) _(PUSCH,c)(i) provided by the higher layer and issignaled to the UE by the base station.

j is 1 in PUSCH transmission/retransmission according to an uplink grantand j is 2 in PUSCH transmission/retransmission according to a randomaccess response. In addition, P_(O) _(_) _(UE) _(_) _(PUSCH,c)(2)=0 andP_(O) _(_) _(NOMINAL) _(_) _(PUSCH,c)(2) =P_(O) _(_) _(PRE)+Δ_(PREAMBLE)_(_) _(Msg3). Parameters P_(O) _(_) _(PRE) and Δ_(PREAMBLE) _(_) _(Mgs3)are signaled by them higher layer.

α_(c)(j) is a pathloss compensation factor and a cell-specific parameterprovided by the higher layer and transmitted as 3 bits by the basestation. α∈{0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1}} when j is 0 or 1 andα_(c)(j)=1 when j is 2. α_(c)(j) is a value signaled to the UE by thebase station.

Pathloss PL_(c) is a downlink pathloss (or signal loss) estimate valuein dBs, calculated by the UE, and is represented asPL_(c)=referenceSignalPower−higher layer filteredRSRP. Here,referenceSignalPower can be signaled to the UE by the base station viathe higher layer.

f_(c)(i) is a value indicating current PUSCH power control adjustmentstate for the subframe index i and can be represented as a currentabsolute value or accumulated value. When accumulation is enabled on thebasis of a parameter provided by the higher layer or a TPC commandδ_(PUSCH,c) is included in a PDCCH along with DCI format 0 for theserving cell C in which CRC is scrambled with temporary C-RNTI,f_(c)(i)=f_(c)(i−1)−δ_(PUSCH,c)(i−K_(PUSCH)) is satisfied.δ_(PUSCH,c)(i−K_(PUSCH)) is signaled through the PDCCH with DCI format0/4 or 3/3A in a subframe i−K_(PUSCH). Here, f_(c)(0) is the first valueafter reset of the accumulated value.

K_(PUSCH) is defined in LTE as follows.

For FDD (Frequency Division Duplex), K_(PUSCH) has a value of 4. As toTDD, K_(PUSCH) has values as shown in Table 2.

TABLE 2 TDD UL/DL subframe number i Configuration 0 1 2 3 4 5 6 7 8 9 0— — 6 7 4 — — 6 7 4 1 — — 6 4 — — — 6 4 — 2 — — 4 — — — — 4 — — 3 — — 44 4 — — — — — 4 — — 4 4 — — — — — — 5 — — 4 — — — — — — — 6 — — 7 7 5 —— 7 7 —

The UE attempts to decode a PDCCH in DCI format 0/4 with C-RNTI thereofor to decode a PDCCH in DCI format 3/3A and a DCI format for SPS C-RNTIwith TPC-PUSCH-RNTI thereof in each subframe in cases other than DRXstate. When DCI formats 0/4 and 3/3A for the serving cell c are detectedin the same subframe, the UE needs to use δ_(PUSCH,c) provided in DCIformat 0/4. When a TPC command decoded for the serving cell c is notpresent, DRX is generated or a subframe having index i is a subframeother than an uplink subframe in TDD, δ_(PUSCH,c) is 0 dB.

Accumulated δ_(PUSCH,c), which is signaled together with DCI format 0/4on a PDCCH, is shown in Table 3. When a PDCCH with DCI format 0 isvalidated through SPS activation or released, δ_(PUSCH,c), is 0 dB.Accumulated δ_(PUSCH,c), which is signaled with DCI format 3/3A on aPDCCH, is one of SET1 of Table 3 or one of SET2 of Table 4, determinedby a TPC-index parameter provided by the higher layer.

TABLE 3 TPC Command Field in Accumulated Absolute δ_(PUSCH,c) [dB] DCIformat 0/3/4 δ_(PUSCH,c) [dB] only DCI format 0/4 0 −1 −4 1 0 −1 2 1 1 33 4

TABLE 4 TPC Command Field in Accumulated δ_(PUSCH,c) DCI format 3A [dB]0 −1 1 1

When the UE reaches maximum transmission power {circumflex over(P)}_(CMAX)(i) in the serving cell c, a positive TPC command is notaccumulated for the serving cell c. Conversely, when the UE reachesminimum transmission power, a negative TPC command is not accumulated.

The following equation 3 is related to uplink power control with respectto a PUCCH in LTE.

$\begin{matrix}{{P_{PUCCH}(i)} = {\min{\begin{Bmatrix}{{{P_{{CMAX},c}(i)},}\mspace{670mu}} \\{P_{0_{—}{PUCCH}} + {PL}_{c} + {h\left( {n_{CQI},n_{HARQ},n_{SR}} \right)} + {\Delta_{F_{—}{PUCCH}}(F)} + {\Delta_{TxD}\left( F^{\prime} \right)} + {g(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equation 3, i indicates a subframe index and c indicates a cellindex. When a UE is configured by a higher layer to transmit a PUCCHover through antenna ports, Δ_(T×D)(F′) is provided to the UE by thehigher layer. In other cases, Δ_(T×D)(F′) is 0. Parameters with respectto a cell having the cell index C will now be described.

P_(CMAX,c)(i) indicates maximum transmission power of a UE, P₀ ₁₃_(PUCCH) is a parameter corresponding to the sum of cell-specificparameters and signaled by a base station through higher layersignaling, PL_(c) is a downlink pathloss (or signal loss) estimate valuecalculated in dBs by the UE and is represented asPL_(c)=referenceSignalPower−higher layer filteredRSRP. h(n) is a valuedepending on PUCCH format, n_(CQI) is the number of information bitswith respect to channel quality information (CQI) and n_(HARQ) indicatesthe number of HARQ bits. In addition, Δ_(F) ₁₃ _(PUCCH)(F) is a relativevalue with respect to PUCCH format 1 a and a value corresponding toPUCCH format #F, which is signaled by the base station through higherlayer signaling. g(i) indicates a current PUCCH power control adjustmentstate of a subframe having index i.

g(0)=0 when P_(O) _(_) _(UE) _(—PUCCH) is changed in the higher layerand g(0)=ΔP_(rampup)+δ_(msg2) otherwise. δ_(msg2) is a TPC commandindicated in a random access response ΔP_(rampup) corresponds to totalpower ramp-up from the first to last preambles, provided by the higherlayer.

When a UE reaches maximum transmission power P_(CMAX,c)(i) in a primarycell, a positive TPC command is not accumulated for the primary cell.When the UE reaches minimum transmission power, a negative TPC commandis not accumulated. The UE resets accumulation when P_(O) _(_) _(UE)_(_) _(PUCCH) is changed by the higher layer or upon reception of arandom access response.

Tables 5 and 6 show δ_(PUCCH) indicated by a TPC command in DCI formats.Particularly, Table 5 shows δ^(PUCCH) indicated in DCI formats otherthan DCI format 3A and Table 6 shows δ_(PUCCH) indicated in DCI format3A.

TABLE 5 TPC Command Field in DCI format 1A/1B/1D/1/2A/2B/2C/2D/2/3δ_(PUCCH) [dB] 0 −1 1 0 2 1 3 3

TABLE 6 TPC Command Field in DCI format 3A δ_(PUCCH) [dB] 0 −1 1 1

The following equation 4 is associated with sounding reference signal(SRS) power control in LTE.

$\begin{matrix}{{P_{{SRS},c}(i)} = {\min{\begin{Bmatrix}{{P_{{CMAX},c}(i)}\mspace{675mu}} \\{{P_{{{SRS}_{—}{OFFSET}},c}(m)} + {10{\log_{10}\left( M_{{SRS},c} \right)}} + {P_{{O_{—}{PUSCH}},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {f_{c}(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Equation 4, i is a subframe index and c is a cell index. Here,P_(CMAX,c)(i) indicates maximum transmission power of a UE and P_(SRS)₁₃ _(OFFSET,c)(m) is a value set by a higher layer. m=0 corresponds totransmission of a periodic sounding reference signal whereas m=0corresponds to transmission of an aperiodic sounding reference signal.M_(SRS,c) is a sounding reference signal bandwidth in the subframehaving index i of the serving cell c, which is represented as the numberof resource blocks.

f_(c)(i) is a value indicating a current PUSCH power control adjustmentstate for subframe index i of the serving cell c and P_(O) _(_)_(PUSCH,c)(j) and α_(c)(j) are as described in Equations 1 and 2.

The sounding reference signal will now be described.

The sounding reference signal includes a constant amplitude zero autocorrelation (CAZAC) sequence. The sounding reference signals transmittedfrom a plurality of user equipments are CAZAC sequencesr^(SRS)(n)=r_(u,v) ^((α))(n) having different cyclic shift values αbased on the following Equation 5.

$\begin{matrix}{\alpha = {2\pi\frac{n_{SRS}^{cs}}{8}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the Equation 5, n_(SRS) ^(cs) is a value set for each user equipmentby the upper layer, and has an integer value between 0 and 7.Accordingly, the cyclic shift value may have eight values depending onn_(SRS) ^(cs).

The CAZAC sequences generated through cyclic shift from one CAZACsequence are characterized in that they have a zero-correlation valuewith the sequences having different cyclic shift values. The soundingreference signals of the same frequency domain can be identified fromone another depending on the CAZAC sequence cyclic shift value by usingthe above characteristic. The sounding reference signal of each userequipment is allocated on the frequency depending on a parameter set bythe base station. The user equipment performs frequency hopping of thesounding reference signal to transmit the sounding reference signal toall of uplink data transmission bandwidths.

Hereinafter, a detailed method for mapping a physical resource fortransmitting a sounding reference signal in an LTE system will bedescribed.

After being multiplied by an amplitude scaling parameter β_(SRS) tosatisfy the transmission power P_(SRS) of the user equipment, thesounding reference signal sequence r^(SRS)(n) is mapped into a resourceelement (RE) having an index of (k, l) from r^(SRS)(0) by the followingEquation 6.

$\begin{matrix}{a_{{{2k} + k_{0}},l} = \left\{ \begin{matrix}{\beta_{SRS}{r^{SRS}(k)}} & {{k = 0},1,\ldots,{M_{{sc},b}^{RS} - 1}} \\0 & {otherwise}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In the Equation 6, k₀ denotes a frequency domain start point of thesounding reference signal, and is defined by the following Equation 7.

$\begin{matrix}{k_{0} = {k_{0}^{\prime} + {\sum\limits_{b = 0}^{B_{SRS}}\;{2M_{{sc},b}^{RS}n_{b}}}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

In the Equation 7, n_(b) denotes a frequency location index. Also, k′₀for a general uplink subframe is defined by the following Equation 8,and k′₀ for an uplink pilot timeslot (UpPTS) is defined by the followingEquation 9.

$\begin{matrix}{k_{0}^{\prime} = {{\left( {\left\lfloor {N_{RB}^{UL}\text{/}2} \right\rfloor - {m_{{SRS},0}\text{/}2}} \right)N_{SC}^{RB}} + k_{TC}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack \\{k_{0}^{\prime} = \left\{ \begin{matrix}{{\left( {N_{RB}^{UL} - m_{{SRS},0}^{\max}} \right)N_{sc}^{RB}} + k_{TC}} & {{{if}\mspace{14mu}\left( {{\left( {n_{f}\mspace{14mu}{mod}\mspace{14mu} 2} \right) \times \left( {2 - N_{SP}} \right)} + n_{hf}} \right){mod}\mspace{14mu} 2} = 0} \\{k_{TC}\mspace{230mu}} & {{otherwise}\mspace{365mu}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

In the Equation 8 and the Equation 9, k_(TC) is a transmission Combparameter signaled to the user equipment through the upper layer and hasa value of 0 or 1. Also, n_(hf) is 0 at the uplink pilot timeslot of thefirst half frame and 0 at the uplink pilot timeslot of the second halfframe. M_(sc,b) ^(RS) is a length, i.e., bandwidth, of a soundingreference signal sequence, which is expressed in a unit of subcarrierdefined as expressed by the following Equation 10.M _(sc,b) ^(RS) =m _(SRS,b) N _(sc) ^(RB)/2   [Equation 10]

In the Equation 10, m_(SRS,b) is a value signaled from the base stationdepending on an uplink bandwidth N_(RB) ^(UL).

The user equipment can perform frequency hopping of the soundingreference signal to transmit the sounding reference signal to all theuplink data transmission bandwidths. The frequency hopping is set by aparameter b_(hop) having a value of 0 to 3 given by the upper layer.

If frequency hopping of the sounding reference signal is not activated,i.e., in case of b_(hop)≧B_(SRS), the frequency location index n_(b) hasa constant value as expressed by the following Equation 11. In theEquation 11, n_(RRC) is a parameter given by the upper layer.n _(b)=└4n _(RRC) /m _(SRS,b)┘mod N _(b)   [Equation 11]

Meanwhile, if frequency hopping of the sounding reference signal isactivated, i.e., in case of b_(hop)<B_(SRS), the frequency locationindex n_(b) is defined by the following Equations 12 and 13.

$\begin{matrix}{n_{b} = \left\{ \begin{matrix}{\left\lfloor {4n_{RRC}\text{/}m_{{SRS},b}} \right\rfloor{mod}\mspace{14mu} N_{b}} & {b \leq b_{hop}} \\{\left\{ {{F_{b}\left( n_{SRS} \right)} + \left\lfloor {4n_{RRC}\text{/}m_{{SRS},b}} \right\rfloor} \right\}{mod}\mspace{14mu} N_{b}} & {otherwise}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack \\{{F_{b}\left( n_{SRS} \right)} = \left\{ \begin{matrix}{{\left( {N_{b}\text{/}2} \right)\left\lfloor \frac{n_{SRS}\mspace{14mu}{mod}\mspace{14mu}\Pi_{b^{\prime} = b_{hop}}^{b}N_{b^{\prime}}}{\Pi_{b^{\prime} = b_{hop}}^{b - 1}N_{b^{\prime}}} \right\rfloor} + \left\lfloor \frac{n_{SRS}\mspace{14mu}{mod}\mspace{14mu}\Pi_{b^{\prime} = b_{hop}}^{b}N_{b^{\prime}}}{2\Pi_{b^{\prime} = b_{hop}}^{b - 1}N_{b^{\prime}}} \right\rfloor} & {{if}\mspace{14mu} N_{b}\mspace{14mu}{even}} \\{\left\lfloor {N_{b}\text{/}2} \right\rfloor\left\lfloor {n_{SRS}\text{/}\Pi_{b^{\prime} = b_{hop}}^{b - 1}N_{b^{\prime}}} \right\rfloor} & {{if}\mspace{14mu} N_{b}\mspace{14mu}{odd}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

n_(SRS) is a parameter that calculates the number of transmission timesof the sounding reference signal and is defined by the followingEquation 14.

$\begin{matrix}{n_{SRS} = \left\{ \begin{matrix}{{{2N_{SP}n_{f}} + {2\left( {N_{SP} - 1} \right)\left\lfloor \frac{n_{s}}{10} \right\rfloor} + \left\lfloor \frac{T_{offset}}{T_{{offset}_{—}\max}} \right\rfloor},} & {{for}\mspace{14mu} 2\mspace{14mu}{ms}\mspace{14mu}{SRS}\mspace{14mu}{periodicity}\mspace{14mu}{of}\mspace{14mu}{TDD}\mspace{14mu}{frame}\mspace{14mu}{structure}} \\{{\left\lfloor {\left( {{n_{f} \times 10} + \left\lfloor {n_{s}\text{/}2} \right\rfloor} \right)\text{/}T_{SRS}} \right\rfloor,}\mspace{185mu}} & {{otherwise}\mspace{445mu}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

In the Equation 14, T_(SRS) is a period of the sounding referencesignal, and T_(offset) denotes subframe offset of the sounding referencesignal. Also, n_(s) denotes a slot number, and n_(f) denotes a framenumber.

A user equipment specific sounding reference signal setup index I_(SRS)for setting the period T_(SRS) of the user equipment specific soundingreference signal and the subframe offset T_(offset) is expressed asillustrated in the following Table 7-10 depending on FDD and TDD. Inparticular, Table 7 illustrates the user equipment specific soundingreference signal configuration index in case of the FDD, and Table 8illustrates the user equipment specific sounding reference signalconfiguration index in case of the TDD. Tables 7 and 8 show periodicityand offset information with respect to triggering type 0, that is, theperiodic SRS.

TABLE 7 SRS Configuration Index SRS Periodicity T_(SRS) SRS I_(SRS) (ms)Subframe Offset T_(offset) 0-1 2 I_(SRS) 2-6 5 I_(SRS) - 2  7-16 10I_(SRS) - 7 17-36 20 I_(SRS) - 17 37-76 40 I_(SRS) - 37  77-156 80I_(SRS) - 77 157-316 160 I_(SRS) - 157 317-636 320 I_(SRS) - 317 637-1023 reserved reserved

TABLE 8 SRS Periodicity T_(SRS) SRS Configuration Index I_(SRS) (ms)Subframe Offset T_(offset) 0 2 0, 1 1 2 0, 2 2 2 1, 2 3 2 0, 3 4 2 1, 35 2 0, 4 6 2 1, 4 7 2 2, 3 8 2 2, 4 9 2 3, 4 10-14 5 I_(SRS) - 10 15-2410 I_(SRS) - 15 25-44 20 I_(SRS) - 25 45-84 40 I_(SRS) - 45  85-164 80I_(SRS) - 85 165-324 160 I_(SRS) - 165 325-644 320 I_(SRS) - 325 645-1023 reserved reserved

TABLE 9 SRS Configuration Index SRS Periodicity T_(SRS,1) SRS SubframeI_(SRS) (ms) Offset T_(offset,1) 0-1 2 I_(SRS) 2-6 5 I_(SRS) - 2  7-1610 I_(SRS) - 7 17-31 reserved reserved

Tables 9 and 10 show periodicity and offset information regardingtriggering type 1, that is, the aperiodic SRS. Particularly, Table 9shows the case of an FDD system and FIG. 10 shows the case of a TDDsystem.

TABLE 10 SRS Configuration SRS Periodicity T_(SRS,1) SRS Index I_(SRS)(ms) Subframe Offset T_(offset,1) 0 2 0, 1 1 2 0, 2 2 2 1, 2 3 2 0, 3 42 1, 3 5 2 0, 4 6 2 1, 4 7 2 2, 3 8 2 2, 4 9 2 3, 4 10-14 5 I_(SRS) - 1015-24 10 I_(SRS) - 15 25-31 reserved reserved

In recent wireless communication systems, there has been discussion oftechniques for flexibly changing usage of resource for downlink oruplink when an eNB divides all available resources into downlinkresources and uplink resources and performs duplex operation using theresources.

The aforementioned method for flexibly changing usage of resources hasthe advantage that optimized resource distribution can be performed whensizes of downlink traffic and uplink traffic are flexibly varied. Forexample, in operations of an FDD system using frequency bands dividedinto a downlink band and an uplink band, an eNB can designate a specificband to a downlink resource or an uplink resource at a specific timethrough an RRC, MAC or physical layer signal for flexible resource usagechange.

Particularly, a TDD system partitions all subframes into uplinksubframes and downlink subframes and uses the uplink subframes anddownlink subframes for uplink transmission of UEs and downlinktransmission of an eNB. Such resource partitioning can be provided aspart of system information according to the uplink/downlink subframeconfigurations of Table 1. New uplink/downlink subframe configurationsmay be provided in addition to the uplink/downlink subframeconfigurations of Table 1. For flexible resource usage change in the TDDsystem, the eNB can designate a specific subframe to a downlink resourceor an uplink resource at a specific time through an RRC, MAC or physicallayer signal.

In LTE systems, a downlink resource and an uplink resource aredesignated through system information. Since the system informationneeds to be transmitted to a plurality of unspecified UEs, operations oflegacy UEs may have problems when the system information is flexiblychanged. Accordingly, it is desirable to transmit information onflexible resource usage change to UEs currently linked to an eNB throughnew signaling, particularly, UE-dedicated signaling, rather than thesystem information. Such new signaling may indicate a configuration of aflexibly changed resource, for example, uplink/downlink subframeconfiguration information different from that indicated through systeminformation in a TDD system.

In addition, such new signaling may include information related to HARQ.Particularly, the new signaling may include a scheduling message andPDSCH/PUSCH transmission timing corresponding thereto, and HARQ timelineconfiguration information for maintaining stable HARQ timeline even ifresource configuration is flexibly changed so as to solve a problem thatHARQ timeline, defined as HARQ-ACK transmission timing, does notcontinue when the HARQ timeline is flexibly changed. In the case of aTDD system, the HARQ timeline configuration information can be providedas an uplink/downlink subframe configuration that is referred to whendownlink HARQ timeline and/or uplink HARQ timeline are defined.

As described above, a UE linked to a system that flexibly changes usageof resources receives information about a resource configuration. In thecase of TDD system, particularly, a UE can acquire the followinginformation at a specific time.

1) Uplink/downlink subframe configuration indicated by systeminformation

2) Uplink/downlink subframe configuration transmitted in order toindicate usage of each subframe through additional signaling

3) Uplink/downlink subframe configuration transmitted to define downlinkHARQ timing, that is, when HARQ-ACK for a PDSCH received at a specifictime will be transmitted

4) Uplink/downlink subframe configuration transmitted to define uplinkHARQ timing, that is, when a PUSCH for an uplink grant received at aspecific time will be transmitted and when a PHICH for a PUSCHtransmitted at a specific time will be received

When a specific UE is linked to an eNB that flexibly changes usage ofresources, the eNB may operate to set an uplink/downlink subframeconfiguration including as many uplink subframes as possible throughsystem information in many cases. This is because flexible change ofsubframes, which are designated as downlink subframes through the systeminformation, to uplink subframes may be restricted. For example, sincelegacy UEs expect and measure CRS transmission in subframes, which aredesignated as downlink subframes through system information, all thetime, serious error can be generated in CRS measurement of the legacyUEs when the downlink subframes are flexibly changed to uplinksubframes. Accordingly, it is desirable that the eNB flexibly changesome uplink subframes to downlink subframes when downlink trafficincreases while configuring a larger number of uplink subframe on thesystem information.

In a TDD system operating according to the aforementioned principle,although uplink/downlink subframe configuration #0 is signaled to a UEthrough system information at a specific time, usage of resources ineach subframe may conform to uplink/downlink subframe configuration #1.

Downlink HARQ timing may be based on uplink/downlink subframeconfiguration #2. This is because HARQ timing can be maintained even ifuplink/downlink subframe configurations are flexibly changed when HARQtiming is based on an uplink/downlink subframe configuration including asmaller number of uplink subframes and a larger number of downlinksubframes such that the number of downlink subframes reaches a maximumnumber to cause a situation in which HARQ-ACK is difficult to transmitand downlink HARQ timing is operated in this situation. Similarly,uplink HARQ timing may be based on an uplink/downlink subframeconfiguration including a larger number of uplink subframes, such asuplink/downlink subframe configuration #0.

As described above, uplink transmission power control of a UE includesopen loop power control (OLPC) and closed loop power control (CLPC). Theformer controls power in such a manner that attenuation of a downlinksignal from an eNB of a cell to which the UE belongs is estimated andcompensated for. For example, OLPC controls uplink power by increasinguplink transmission power when downlink signal attenuation increases asa distance between the UE and the eNB increases. The latter controlsuplink power in such a manner that the eNB directly transmitsinformation (i.e. a control signal) necessary to control uplinktransmission power.

However, these conventional uplink power control methods do not considera UE linked to an eNB that flexibly changes usage of resources. When theconventional power control methods are used although specific uplinktransmission is carried out in an uplink subframe to which flexibleresource usage change is applied, uplink transmission performance may beseriously deteriorated since interference environments are remarkablychanged due to downlink transmission of a neighboring cell and the like.

For such a reason, LTE discusses a method of designating a plurality ofsubframe sets and applying different power control methods to respectivesubframe sets. Information on the plurality of subframe sets may beprovided to UEs through higher layer signaling such as RRC signaling.Particularly, the information may be provided in connection withinformation on subframe sets used for other purposes or independentlyRRC-signaled.

For convenience of description, it is assumed that two subframe sets aresignaled. The subframes are respectively referred to as subframe set #1and subframe set #2 in the following. Subframe set #1 and subframe set#2 can be defined as L-bit subframe bitmaps. Particularly, subframe set#1 and subframe set #2 can respectively correspond to static subframesand flexible subframes.

FIG. 8 illustrates one radio frame divided into subframe set #1 andsubframe set #2.

Referring to FIG. 8, a static subframe can refer to a conventionalsubframe to which flexible resource usage change is not applied. Aflexible subframe can refer to a subframe to which flexible resourceusage change is applied or can be applied. That is, an interferenceenvironment during uplink transmission of a UE may be remarkably variedin the flexible subframe, differently from the static subframe, and thusit is preferable to apply a separate uplink power control method to theflexible subframe.

FIG. 8 illustrates a case in which cell B (neighboring cell) changessubframes #(n+3), #(n+4), #(n+8) and #(n+9) to downlink subframes in astate in which cell A (serving cell) and cell B set uplink/downlinksubframe configuration #0 (that is, DSUUUDSUUU) through systeminformation.

In this case, cell A can configure subframe set #1 and subframe set #2for UEs belonging thereto, as shown in FIG. 8, and allow the UEs toapply different power control methods to the subframe sets. That is, ifinter-cell coordination is possible, when a specific cell flexiblychanges usage of resources, neighboring cells can appropriatelyconfigure subframe sets in consideration of flexible resource usagechange of the specific cell. Alternatively, it is predetermined thatonly predetermined subframe set configurations are applied between cellssuch that flexible resource usage change can be applied to a specificsubframe set (e.g. subframe set #2 in FIG. 8) only.

Specifically, when a conventional PUSCH PC in a specific subframe set(e.g. subframe set #1 which corresponds to flexible subframes) isapplied to another specific subframe set (e.g. subframe set #1 which isa static subframe), performance deterioration may occur due to a largeinterference difference between the subframe sets. Accordingly, it isdesirable to respectively apply separate PUSCH power control processesto the subframe sets.

The present invention sets a plurality of SRS power control processes,similarly to setting a plurality of PUSCH power control processes for aspecific UE. Particularly, the present invention can establish arelationship between a specific SRS power control process and a specificPUSCH power control process.

For example, PUSCH power control process #1 can be associated with SRSpower control process #1 and PUSCH power control process #2 can beassociated with SRS power control process #2. Here, linkage may meanthat at least one of parameters {P_(CMAX,c)(i), P_(SRS) _(_)_(OFFSET,c)(m), M_(SRS,c), P_(O) _(_) _(PUSCH,c)(j), α_(c)(j), PL_(c),f_(c)(i)} related to an SRS power control process is identical to thecorresponding parameter of a PUSCH power control process associated withthe SRS power control process or is determined in association with thecorresponding parameter according to a specific function. Specifically,{P_(O) _(_) _(PUSCH,c)(j), α_(c)(j), PL_(c), f_(c)(i)} can be set to beidentical to corresponding parameters of the corresponding PUSCH powercontrol process. P_(SRS) _(_) _(OFFSET,c)(m) may be set as anindependent value for each SRS power control process or set as a commonvalue for some SRS power control processes.

Each SRS power control process may be set to triggering type ( ), thatis, periodic SRS (P-SRS) or triggering type 1, that is, aperiodic SRS(A-SRS). While a plurality of A-SRS configurations may be presentaccording to triggering bit, periodicity T_(SRS,1) and subframe offsetT_(offset,1) of an A-SRS can be designated to be commonly applied to allA-SRS configurations. A subframe set defined by periodicity T_(SRS,1)and subframe offset T_(offset,1) of the A-SRS is referred to as an A-SRSsubframe set.

The present invention additionally considers a scheme in which A-SRSsubframe set information is independently set for each A-SRSconfiguration as well as a scheme in which the A-SRS subframe set iscommonly provided for all A-SRS configurations through RRC signaling,and provides a method for UE operation regarding triggering of A-SRStransmission according to an SRS power control process.

The present invention assumes a case in which a UE receives informationon specific power control subframe sets, such as subframe set #1 (e.g.“static subframes”) and subframe set #2 (e.g. “flexible subframes”),through higher layer signaling. Such power control subframe setinformation and the aforementioned A-SRS subframe set information may beprovided as separate pieces of information or the power control subframesets may be associated with A-SRS subframe sets in such a manner thatpower control subframe set #1 corresponds to A-SRS subframe set #0 andpower control subframe set #2 corresponds to A-SRS subframe set #1.

While two power control subframe sets #1 and #2 are configured for theUE in the following description, three or more power control subframesets may be configured in the present invention. In addition, while thetwo power control subframe sets may respectively correspond to staticsubframes and flexible subframes, this is exemplary and thus each powercontrol subframe set may be set to an arbitrary independent subframe setthrough RRC and the UE can perform uplink transmission (e.g. PUSCHtransmission) in a power control subframe set according to an uplinkpower control process corresponding thereto.

In addition, power control subframe set #1 can be set to staticsubframes which are uplink subframes all the time. On the other hand,power control subframe set #2 can be set to subframes including not onlysubframes, which are designated as downlink subframes through systeminformation but may be flexibly changed to uplink subframes, but alsolatent flexible subframes, which are designated as uplink subframesthrough the system information but reconfigured as downlink subframesthrough higher layer signaling or physical layer signaling and thenchanged to uplink subframes according to reconfiguration information.

Embodiments to which the present invention is applied will now bedescribed in detail.

First Embodiment

In the first embodiment of the present invention, A-SRS subframe setinformation is commonly provided for all A-SRS configurations.Particularly, A-SRS transmission is performed according to the followingmethod 1) or method 2) in the first embodiment of the present invention.

Method 1)—Implicit Signaling

When an A-SRS triggering message is received in an n-th subframe, thecorresponding A-SRS is transmitted in an m-th subframe initiallybelonging to an A-SRS subframe set after an (n+k)-th subframe (e.g.(n+4)-th subframe). A-SRS transmission power is determined using a powercontrol process applied to power control subframe set #1 or powercontrol subframe set #2, to which the m-th subframe belongs, and theA-SRS is transmitted with the transmission power.

Here, A-SRS power control processes respectively pre-associated withpower control subframe set #1 and power control subframe set #2 may besignaled through an RRC layer. Alternatively, power control processesrespectively pre-associated with power control subframe set #1 and powercontrol subframe set #2 may be signaled in such a manner that onlyinformation on a specific PUSCH power control process is providedthrough the RRC layer and information on additional association of aspecific A-SRS power control process and each PUSCH power controlprocess is provided to define the A-SRS power control process.

That is, an A-SRS power control process associated with a PUSCH powercontrol process corresponding to the power control subframe set to whichthe m-th subframe belongs is applied.

Method 2)—Explicit Signaling

Distinguished from method 1), power control parameters or a powercontrol process index applied per A-SRS triggering field may be setthrough RRC signaling. For example, at least one of {P_(CMAX,c)(i),P_(SRS) _(_) _(OFFSET,c)(m), P_(O) _(—PUSCH,c) (j), α_(c)(j)} can be setper A-SRS triggering field. In this case, the at least one parameter canbe set in such a manner that the parameter is associated with a relatedparameter of a specific PUSCH power control process.

In addition, with respect to TPC f_(c)(i), a common single TPCaccumulation process can be applied to all power control processes. Inthis case, f_(c)(i) is applied to determine corresponding A-SRStransmission power according to the corresponding single TPC command. Ifmultiple TPC parameters are respectively present for specific powercontrol processes, a TPC parameter applied per A-SRS triggering fieldmay be set through RRC signaling.

As described above, since power control parameters or a power controlprocess index are explicitly set per A-SRS triggering field, when theA-SRS triggering message is received in the n-th subframe, thecorresponding A-SRS is transmitted in the m-th subframe initiallybelonging to the A-SRS subframe set after the (n+k)-th subframe (e.g.(n+4)-th subframe).

Such explicit association signaling can be defined as shown in Table 11.Table 11 shows an A-SRS triggering field having 2 bits.

TABLE 11 Value of SRS request field Description ‘00’ No type 1 SRStrigger ‘01’ The 1^(st) SRS parameter set configured by higher layersand PC parameters used for PUSCH in the subframe (on which the SRStriggered by this DCI is transmitted) ‘10’ The 2^(nd) SRS parameter setand PC parameter set 1 configured by higher layers ‘11’ The 3^(rd) SRSparameter set and PC parameter set 2 configured by higher layers

Fields values “10” and “11” of Table 11 respectively describe powercontrol parameter set #1 (i.e. power control subframe set #1) and powercontrol parameter set #2 (i.e. power control subframe set #2). Fieldvalue “01” describes implicit signaling of method 1). While Table 11shows the 2-bit triggering field, signaling can be normalized andextended in a similar form even in the case of a triggering field of 3or more bits.

In DCI having a 1-bit triggering field, field values and attributesthereof can be defined as shown in Table 12 or 13.

TABLE 12 Value of SRS request field Description ‘0’ No type 1 SRStrigger ‘1’ The 1^(st) SRS parameter set configured by higher layers andPC parameters used for PUSCH in the subframe (on which the SRS triggeredby this DCI is transmitted)

TABLE 13 Value of SRS request field Description ‘0’ No type 1 SRStrigger ‘1’ The 2^(nd) SRS parameter set and PC parameter set 1configured by higher layers

Tables 12 and 13 show two different embodiments. That is, field value“0” indicates “no type 1 SRS trigger”, that is, no A-SRS transmission,and only field value “1” can be configured by RRC, and thus RRCconfiguration is provided such that A-SRS transmission is performedaccording to method 1 in Table 10. In this case, when a UE receivesfield value “1” through the corresponding DCI, the UE determinestransmission power using a PUSCH power control process or a powercontrol parameter corresponding to the power control subframe set towhich a subframe in which the corresponding A-SRS is transmitted belongsand transmits the A-SRS with the transmission power.

When the UE receives field value “1” of FIG. 13, the UE determines A-SRStransmission power using power control parameter set #1 (or powercontrol subframe set #1) all the time irrespective of the power controlsubframe set to which the subframe in which the corresponding A-SRS istransmitted belongs and transmits the A-SRS with the determinedtransmission power. In FIG. 13, power control parameter set #2 may beprovided as an RRC configuration for field value “1”.

Alternatively, field value “1” may be defined to conform to a specificfield value of a triggering field of two or more bits, as shown in Table11. For example, field value “01” of Table 11 is automatically definedas RRC configuration of field value “1”. Here, the relationship betweenDCI having a 1-bit A-SRS triggering field and DCI having an A-SRStriggering field having two or more bits can be predefined or providedthrough RRC signaling.

When multiple pieces of DCI having an N-bit SRS triggering field arepresent, the information of Tables 11, 12 and 13 may be RRC-signaledsuch that the information is commonly used for the DCI or separateinformation may be independently RRC-signaled per DCI. Alternatively,multiple tables with respect to the relationship between an SRStriggering field and a power control process, such as Tables 11, 12 and13, are established and a corresponding table is applied according towhether DCI is detected from a UE-specific search space or a commonsearch space and whether the DCI is detected from a normal PDPCCH orthrough an enhanced PDCCH (EPDCCH) received through a data region.

The UE may be configured to determine A-SRS transmission power usingonly a power control parameter set corresponding to the lowest (orhighest) index all the time and to transmit the A-SRS with the power,instead of being RRC-signaled RRC configuration for a specific fieldvalue (e.g. field value “1”) as shown in Tables 12 and 13. For example,if the UE is configured to use the power control parameter setcorresponding to the lowest index while indices of 0 to N are assignedto power control parameter sets, the UE can operate to determine A-SRStransmission power according to power control parameter set #1 and totransmit the A-SRS with the transmission power when a specific fieldvalue is dynamically triggered. Accordingly, RRC signaling overhead canbe reduced. This is because, when an eNB intends to configure a specificpower control parameter set, A-SRS transmission power can be determinedthrough dynamic signaling according to a corresponding field value bysetting/re-setting the specific power control parameter set to thelowest (or highest) index all the time.

Second Embodiment

In the second embodiment of the present invention, A-SRS subframe setinformation is independently provided per A-SRS configuration.Particularly, A-SRS transmission is performed according to the followingmethod 3 or method 4 in the second embodiment of the present invention.

Method 3)—Implicit Signaling

When an A-SRS triggering field is received in the n-th subframe, thecorresponding A-SRS is transmitted in the m-th subframe initiallybelonging to an A-SRS subframe set which is separately set to thecorresponding A-SRS triggering field after the (n+k)-th subframe (e.g.(n+4)-th subframe). A-SRS transmission power is determined using a powercontrol process applied to power control subframe set #1 or powercontrol subframe set #2, to which the m-th subframe belongs and theA-SRS is transmitted with the transmission power.

Here, A-SRS power control processes respectively pre-associated withpower control subframe set #1 and power control subframe set #2 may besignaled through an RRC layer. Alternatively, power control processesrespectively pre-associated with power control subframe set #1 and powercontrol subframe set #2 may be signaled in such a manner that onlyinformation on a specific PUSCH power control process is providedthrough the RRC layer and information on additional association of aspecific A-SRS power control process and each PUSCH power controlprocess is provided to define the A-SRS power control process. An A-SRSpower control process associated with a PUSCH power control processcorresponding to the power control subframe set to which the m-thsubframe belongs is applied.

Method 4)—Explicit Signaling

Distinguished from method 1), an A-SRS subframe set and power controlparameters (or a power control process index) applied per A-SRStriggering field may be set through RRC signaling. For example, at leastone of {P_(CMAX,c)(i), P_(SRS) _(_) _(OFFSET,c)(m), P_(O) _(_)_(PUSCH,c)(j), α_(c)(j)} can be set per A-SRS triggering field. In thiscase, the at least one parameter can be set in such a manner that theparameter is associated with a related parameter of a specific PUSCHpower control process. In addition, with respect to TPC f_(c)(i), acommon single TPC accumulation process can be applied to all powercontrol processes. In this case, f_(c)(i) is applied to determinecorresponding A-SRS transmission power according to the correspondingsingle TPC command. If multiple TPC parameters are respectively presentfor specific power control processes, a TPC parameter applied per A-SRStriggering field may be set through RRC signaling.

As described above, since power control parameters or a power controlprocess index are explicitly set per A-SRS triggering field, when theA-SRS triggering message is received in the n-th subframe, thecorresponding A-SRS is transmitted in the m-th subframe initiallybelonging to an A-SRS subframe set, which is separately set to thetriggering field of the A-SRS, after the (n+k)-th subframe (e.g.(n+4)-th subframe).

In addition to the aforementioned methods, when an A-SRS triggeringmessage is received in the n-th subframe irrespective of A-SRS subframeconfiguration (or in a specific situation such as a case in which noA-SRS subframe configuration is present), the corresponding A-SRS istransmitted in a designated (n+k′)-th subframe (here, k′ is 4 or ispredefined or designated through dynamic signaling or semi-staticsignaling) all the time using a power control process applied to powercontrol subframe set #1 or power control subframe set #2, to which the(n+k)′-th subframe belongs.

A-SRS power control processes respectively pre-associated with powercontrol subframe set #1 and power control subframe set #2 may besignaled through RRC. Alternatively, power control processesrespectively pre-associated with power control subframe set #1 and powercontrol subframe set #2 may be defined in such a manner that onlyinformation on a specific PUSCH power control process is providedthrough RRC and information on additional association of a specificA-SRS power control process and each PUSCH power control process isprovided to defined the A-SRS power control process. That is, an A-SRSpower control process associated with a PUSCH power control processcorresponding to the power control subframe set to which the (n+k′)-thsubframe belongs is applied.

Alternatively, when an A-SRS is triggered in the n-th subframeirrespective of A-SRS subframe configuration (or in a specific situationsuch as a case in which no A-SRS subframe configuration is present), theA-SRS can be transmitted in an m-th subframe initially belonging topower control subframe set #p (p=1, 2, . . . , the value of p beingspecified according to RRC configuration or fixed to a specific value)after the (n+k)-th subframe and SRS power can be determined according toa power control process corresponding to power control subframe set #p.Here, RRC configuration for a power control subframe set number, such asp, may be set per A-SRS triggering field and/or per specific DCI, or maybe commonly applied to all A-SRSs.

The A-SRS power control processes pre-associated with power controlsubframe set #1 and power control subframe set #2 may be signaledthrough RRC. Alternatively, power control processes pre-associated withpower control subframe set #1 and power control subframe set #2 may besignaled in such a manner that only information on a specific PUSCHpower control process is provided through RRC signaling and informationon additional association of a specific A-SRS power control process andeach PUSCH power control process is provided to define the specificA-SRS power control process. That is, an A-SRS power control processassociated with a PUSCH power control process corresponding to the powercontrol subframe set to which the (n+k)-th subframe belongs is applied.

Alternatively, when an A-SRS is triggered in the n-th subframeirrespective of A-SRS subframe configuration (or in a specific situationsuch as a case in which no A-SRS subframe configuration is present), theA-SRS can be transmitted in then m-th subframe belonging to powercontrol subframe set #q (q can be automatically determined from amongindices 1, 2, . . . according to a power control subframe set whichinitially appears after the (n+k)-th subframe) which initially appearsafter the (n+k)-th subframe (e.g. (n+4)-th subframe) and SRS power canbe determined according to a power control process corresponding topower control subframe set #q. That is, q is determined based on a powercontrol subframe set which initially appears after the (n+k)-thsubframe, rather than being fixed, and thus q can be varied according toA-SRS triggering time.

In the case of DCI including a 1-bit A-SRS triggering field, the A-SRStriggering field can have only one field value (e.g. field value “1”indicating A-SRS triggering) and thus an implicit method such as method1 is preferably used.

Alternatively, an independent operation such as method 3 or method 4 maybe performed for each A-SRS triggering field present per DCI. That is,method 3 or method 4 may be applied per A-SRS triggering field inspecific DCI or applied for different pieces of DCI.

Furthermore, it is possible to consider a method for improving SRStransmission power flexibility of a network by simultaneously applyingmethod 3 or method 4 to different pieces of DCI and to DCI havingmultiple triggering fields.

According to the aforementioned methods, it is possible to achievestable SRS reception by applying SRS transmission power control persubframe in an environment in which subframes may have differentinter-cell interference levels, such as an environment to which theaforementioned flexible resource usage change is applied.

The above-described A-SRS related transmission power control can also beapplied to a periodic SRS, that is, P-SRS, which will be described as aseparate embodiment.

Third Embodiment

In the third embodiment of the present invention, it is assumed that aneNB provides a plurality of P-SRS configurations to a UE through RRCsignaling.

In the third embodiment of the present invention, each P-SRSconfiguration is associated with a specific power control process andthe associated power control process uses parameters identical to atleast one of parameters such as {P_(O) _(_) _(PUSCH,c)(j), α_(c)(j).PL_(c), f_(c)(i)} or partially changes finally applied values accordingto a specific function while using the parameters. Each P-SRSconfiguration may be set to conform to an independent power controlprocess.

That is, power control parameter set #1 (i.e. power control subframe set#1) and power control parameter set #2 (i.e. power control subframe set#2) are selectively associated with a P-SRS configuration such that theUE can operate to determine P-SRS transmission power using power controlparameter set #p for a PUSCH all the time and to transmit thecorresponding P-SRS using the transmission power when only one P-SRSconfiguration is set for the UE.

Here, power control parameter set #p for a PUSCH may be a power controlparameter set having the lowest (or highest) index and may be used todetermine P-SRS transmission power and to transmit the correspondingP-SRS. For example, when indices of 0 to N are respectively assigned topower control parameter sets and the power control parameter set havingthe lowest index is determined to be used all the time, P-SRStransmission power can be determined using power control parameter set#1 and the corresponding P-SRS can be transmitted with the transmissionpower. In this case, the quantity of RRC signaling information for thecorresponding P-SRS configuration can be reduced.

The UE may operate to use power control parameter set #1 correspondingto power control subframe set #1 for a PUSCH in a specific subframe andto use power control parameter set #2 corresponding to power controlsubframe set #2 for an SRS in the same subframe.

A specific power control process (e.g. a specific power control subframeset and power control related parameters) that can be associated witheach P-SRS configuration and/or other parameters can be set toindependent values per P-SRS configuration. Here, P-SRS periodicityT_(SRS) may not be a cell-speci1fic parameter. That is T_(SRS) may be aUE-specific parameter and may be set to different values for respectiveP-SRS configurations. When two or more P-SRS configurations havingdifferent periodicities and/or offsets are set, UE operation in a casein which P-SRS transmission timings according to two or more P-SRSconfigurations overlap in a specific subframe may be determined toconform to at least one of the following methods or the correspondingmethod may be set through RRC signaling.

a) A P-SRS, to which parameters according to a P-SRS configurationhaving the longest periodicity and/or a power control processcorresponding to the P-SRS configuration are applied, is transmitted andP-SRS transmissions according to other P-SRS configurations are ignored(that is, dropped). This method has the advantage that SRS transmissionsaccording to various P-SRS configurations can be uniformly performed byproviding highest transmission priority to the P-SRS having the longestperiodicity such that P-SRSs having shorter periodicities are droppedand then transmitted at the next transmission timing.

b) On the assumption that indices are respectively assigned to P-SRSconfigurations, a P-SRS, to which parameters according to a P-SRSconfiguration having the lowest (or highest) index and/or a powercontrol process corresponding to the P-SRS configuration are applied, istransmitted and P-SRS transmissions according to other P-Sconfigurations are dropped.

c) A P-SRS, to which parameters of a specific P-SRS configurationassociated with a power control subframe set corresponding to a currentsubframe and/or a power control process corresponding to the specificP-SRS configuration are applied, is transmitted and P-SRS transmissionsaccording to other P-SRS configurations are dropped. SRS transmissioncan be performed according to whether the current subframe is a staticsubframe or a flexible subframe using this method.

d) A P-SRS, to which parameters of a specific P-SRS configurationassociated with a predefined (or set through RRC signaling) specificpower control subframe set (e.g., power control subframe setcorresponding to a static subframe) and/or a power control processcorresponding to the specific P-SRS configuration are applied, istransmitted all the time and P-SRS transmissions according to otherP-SRS configurations are dropped.

e) All P-SRS transmissions in a corresponding subframe may be dropped.However, when even an A-SRS needs to be transmitted in the correspondingsubframe, it is desirable to transmit the A-SRS.

Obviously, methods a to e can be combined and applied. In this case,priority of application of the methods can be defined. For example,methods a and b can both be applied. This scheme may be implemented insuch a manner that the method a is applied first, when multiple P-SRSconfigurations have the same longest periodicity, only an SRS accordingto a P-SRS configuration having a lower (or higher) index from among theP-SRS configurations is transmitted and other P-SRSs are dropped.

Alternatively, the methods c and b can be applied. When the method c isapplied first, this scheme may be implemented in such a manner that,when two or more P-SRS configurations are associated with a specificpower control subframe set to which a current subframe belongs, only anSRS according to a P-SRS configuration having a lower (or higher) indexfrom among the P-SRS configurations is transmitted and other P-SRSs aredropped.

Alternatively, operation may be performed in the order of a→c→b. Thatis, when two or more P-SRS configurations having the longest periodicityare selected, an SRS according to a P-SRS configuration associated witha specific power control subframe set to which a current subframebelongs is transmitted. If multiple P-SRS configurations are associatedwith the specific power control subframe set to which the currentsubframe belongs, an SRS according to a P-SRS configuration having thelowest (or highest) index from among the multiple P-SRS configurationsis transmitted.

Alternatively, application priority may be determined in the order ofc→a→b. In this case, a power control subframe set to which a currentsubframe belongs is checked for the first time. When two or more P-SRSconfigurations are associated with the power control subframe set towhich the current subframe belongs, a P-SRS configuration having alonger periodicity is detected from the two or more P-SRSconfigurations. When two or more P-SRS configurations have longerperiodicities, an SRS according to a P-SRS configuration having thelowest (or highest) index is transmitted.

Fourth Embodiment

It is assumed that an eNB provides one P-SRS configuration to a UEthrough RRC signaling in the fourth embodiment of the present invention.

The eNB can enable the UE to transmit a P-SRS according to specific SRSconfiguration parameters previously associated with a power controlsubframe set to which a subframe in which SRS transmission is performedaccording to the corresponding P-SRS configuration belongs and/or thecorresponding power control process. That is, the eNB can enable the UEto perform SRS transmission according to SRS related power controlparameters and/or transmission power control depending on whether thecurrent SRS transmission subframe according to the corresponding P-SRSconfiguration is a static subframe or a flexible subframe.

According to this method, at least one of the SRS related power controlparameters {P_(CMAX,c)(i), P_(SRS) _(_) _(OFFSET,c)(m), M_(SRS,c), P_(O)_(_) _(PUSCH,c)(j), α_(c)(j), PL_(c), f_(c)(i)} can be varied accordingto the type of the SRS transmission subframe.

For example, a P-SRS can be transmitted using parameters identical to atleast one of parameters associated with a power control subframe set towhich a current subframe belongs, such as {P_(O) ₁₃ _(PUSCH,c)(j),α_(c)(j), PL_(c), f_(c)(i)}, or by partially changing finally appliedvalues according to a specific function while using the parameter.

Information to be used for power control for P-SRS configurations can beprovided in one of the following forms through RRC signaling.

i) Power control parameters related to a PUSCH in a subframe in which aP-SRS is transmitted

ii) Power control parameter set #1 (i.e. power control subframe set #1)

iii) Power control parameter set #2 (i.e. power control subframe set #2)

If two or more power control parameter sets can be configured, an optionsuch as power control parameter set #3 can be added.

It is obvious that basic restrictions can be imposed on the aboveembodiments such that a subframe in which an SRS is transmitted is usedto transmit the SRS only when the subframe is an uplink subframe (and/ora special subframe) according to flexible resource usage change.

In addition, it is obvious that basic restrictions can be imposed on theabove embodiments such that a subframe in which an SRS is transmitted isused to transmit the SRS only when the subframe is an uplink subframe ora special subframe according to flexible resource usage change. That is,power control subframe sets can include a special subframe and can bedesignated/configured to include a combination of a special subframe anda normal uplink subframe.

Particularly, while the special subframe includes UpPTS for uplinktransmission, a PUSCH is not transmitted and only an SRS can betransmitted in the UpPTS.

However, when a subframe for SRS transmission is a special subframe, apower control parameter set for a PUSCH is present although the PUSCHcannot be transmitted in the special subframe in the present invention.Accordingly, a UE can determine SRS transmission power using the powercontrol parameter set for the PUSCH.

Fifth Embodiment

While a minimum P-SRS periodicity in a TDD system is 2 ms as shown inTable 8, the minimum P-SRS periodicity is 1 ms, as shown in Table 14, inthe fifth embodiment of the present invention for more flexibleutilization of P-SRS configuration.

T_(offset), a factor that determines SRS transmission timing, can be setto a larger number of values, as shown in Table 14, as compared to acase in which the minimum periodicity is 2 ms. Table 14 is exemplary andmodifications for improving P-SRS configuration flexibility are includedin the scope of the present invention.

TABLE 14 SRS Configuration SRS Periodicity T_(SRS) SRS Index I_(SRS)(ms) Subframe Offset T_(offset) Reference_Index + 0 1 0, 1, 2Reference_Index + 1 1 0, 1, 3 Reference_Index + 2 1 0, 1, 4Reference_Index + 3 1 0, 2, 3 Reference_Index + 4 1 0, 2, 4Reference_Index + 5 1 0, 3, 4 Reference_Index + 6 1 1, 2, 3Reference_Index + 7 1 1, 2, 4 Reference_Index + 8 1 1, 3, 4Reference_Index + 9 1 2, 3, 4 Reference_Index + 10 1 0, 1, 2, 3Reference_Index + 11 1 0, 1, 2, 4 Reference_Index + 12 1 0, 1, 3, 4Reference_Index + 13 1 0, 2, 3, 4 Reference_Index + 14 1 1, 2, 3, 4

As an example of network operation, the present embodiment can be usedto allow an eNB to detect an approximate reception power level throughP-SRS transmission according to different P-SRS configurations when twoor more P-SRSs (e.g. P-SRS configurations for PUSCH scheduling in astatic subframe or a flexible subframe) to which different SRS powercontrol processes according to a plurality of P-SRS configurations areapplied are configured to be periodically transmitted.

When the eNB detects that reception sensitivity of an SRS to which aspecific P-SRS configuration is applied increases or decreases from anaverage estimate to a specific level or more (or for more accuratefrequency selective scheduling), the eNB can trigger an A-SRS thatconforms to a specific power control process such that a UE canaperiodically transmit the A-SRS at the request of the eNB. This methodcan enable smooth frequency selective scheduling and link adaptationeven in a situation in which flexible resource usage change occurs.

Sixth Embodiment

When a PUSCH needs to be transmitted in a subframe in which an SRS istransmitted, a UE can be configured to transmit both the PUSCH and theSRS in the same subframe. In this case, the UE operates according to atleast one of the following methods or the corresponding method is setthrough RRC signaling when different power control processes are appliedto the PUSCH and SRS or a transmission power difference between thePUSCH and the SRS corresponds to a specific level or more due to a largetransmission power offset value and the like.

A) When a transmission power difference between a PUSCH and an SRS to betransmitted in the corresponding subframe is larger than a predeterminedvalue or a value provided through RRC signaling, the UE transmits onlyone of the PUSCH and the SRS and drops the other. When it is necessaryto transmit only the PUSCH that is data information without uplinkcontrol information, the UE can drop the PUSCH and transmit only theSRS. When the PUSCH needs to be transmitted with the uplink controlinformation, for example, when a PUCCH is piggybacked on the PUSCH, theUE can drop the SRS and transmit only the PUSCH.

B) When a PUCCH and an SRS need to be simultaneously transmitted in aspecific subframe and a transmission power difference between the PUCCHand the SRS is larger than a predetermined value or a value providedthrough RRC signaling, the UE transmits only one of the PUCCH and theSRS and drops the other.

C) When a PUSCH, a PUCCH and an SRS need to be simultaneouslytransmitted in a specific subframe and a transmission power differencebetween the PUCCH or PUCCH and the SRS is larger than a predeterminedvalue or a value provided through RRC signaling, the UE dropstransmission of the SRS (or the PUSCH and PUCCH) and transmits the PUSCHand PUCCH together (or the SRS alone).

D) The UE transmits the SRS and drops other uplink transmissions orperforms other uplink transmissions and drops the SRS only when an SRSis associated with a specific power control subframe set (e.g., a staticsubframe).

In methods A) to D), the UE may be configured to report thecorresponding transmission power difference value (and/or information ondropping) to the eNB. The transmission power difference value report maybe defined to be included in the PUSCH transmitted in the correspondingsubframe (or transmitted according to the following initial uplinkgrant) through a specific format in the data payload of the PUSCH andtransmitted. Otherwise, the transmission power difference value may beincluded in a PUSCH power headroom report (PHR) or reported therewithwhen a corresponding event is generated. Alternatively, the transmissionpower difference value may be reported through an additional uplinktransmission format, and such report can be periodically performed oraperiodically performed upon generation of a corresponding event.

Seventh Embodiment

The seventh embodiment of the present invention describes a method ofdetermining N_(symb) ^(PUSCH) (or N_(symb) ^(PUSCH-inital)), whichindicates the number of symbols to which a PUSCH is mapped, when a UEattempts to transmit the PUSCH.

Referring to FIG. 9, determination of N_(symb) ^(PUSCH) is affected by avalue NSRS according to cell-specific SRS configuration. When a currentsubframe in which the UE attempts to transmit the PUSCH corresponds to asubframe in which an SRS can be cell-specifically transmitted, NSRS canbe set to 1. Here, the subframe in which the SRS can becell-specifically transmitted can be provided through RRC signalingcorresponding to higher layer signaling.

That is, one cell-specific SRS configuration is signaled to UEs withinthe corresponding cell, and each UE in the cell checks whether a PUSCHtransmission subframe corresponds to the cell-specific SRS subframe whenattempting to transmit a PUSCH and applies rate matching such that PUSCHdata is not mapped to the last symbol (i.e. symbol on which the SRS canbe transmitted) of the corresponding subframe when the PUSCHtransmission subframe corresponds to the cell-specific SRS subframe.Since a PUSCH transmitted from a UE is generally sent to an eNB of aserving cell, the serving cell eNB operates on the basis of only onecell-specific SRS configuration.

However, when a plurality of P-SRS configurations is applied to aspecific UE, as in the present invention, the cell-specific SRS subframeconfiguration is applied to the plurality of P-SRS configurations per UEand thus the number of subframes indicated by the cell-specific SRSsubframe configuration may excessively increase. That is, as the numberof subframes included in the cell-specific SRS subframe configurationincreases, rate matching of the last SC-FDMA symbol during PUSCHtransmission becomes frequent and thus throughput may be reduced. Tosolve this, the seventh embodiment of the present invention sets an SRSsubframe configuration UE-specifically instead of cell-specifically andsets a plurality of UE-specific SRS subframe configurations for aspecific UE.

That is, a plurality of UE-specific SRS subframe configurations can besignaled to a UE through UE-specific RRC signaling and the UE candetermine a UE-specific SRS subframe configuration to be used for PUSCHrate matching when transmitting a PUSCH according to an uplink grant,from among the plurality of UE-specific SRS subframe configurations,through the following methods (X) and (Y).

(X) PUSCH rate matching is performed in subframes obtained through unionof the plurality of UE-specific SRS subframe configurations RRC-signaledto the UE.

(Y) A UE-specific SRS subframe configuration related to subframes inwhich PUSCH rate matching will be performed is flexibly indicatedthrough specific DCI in a corresponding uplink grant. Here, the method(X) may also be applied. That is, the UE can be flexibly instructed toperform PUSCH rate matching in subframes obtained through union of allor part of the plurality of UE-specific SRS subframe configurationsRRC-signaled to the UE. Union of some SRS subframe configurations may bepreset through RRC signaling as a configuration for a specific field ofthe corresponding DCI.

In addition, when the eNB signals a plurality of UE-specific SRSsubframe configurations to a specific UE through RRC signaling,restrictions may be imposed such that subframes obtained through unionof the UE-specific SRS subframe configurations are included in subframesets indicated in cell-specific SRS subframe configurations applied tolegacy UEs at least in the corresponding cell. When SRS subframeconfigurations that do not satisfy the restrictions are signaled to theUE, the UE may ignore the SRS subframe configurations and perform PUSCHrate matching according to the same cell-specific SRS subframeconfigurations as those applied to the legacy UEs.

FIG. 10 is a block diagram for an example of a communication deviceaccording to one embodiment of the present invention.

Referring to FIG. 10, a communication device 1000 may include aprocessor 1010, a memory 1020, an RF module 1030, a display module 1040,and a user interface module 1050.

Since the communication device 1000 is depicted for clarity ofdescription, prescribed module(s) may be omitted in part. Thecommunication device 1000 may further include necessary module(s). And,a prescribed module of the communication device 1000 may be divided intosubdivided modules. A processor 1010 is configured to perform anoperation according to the embodiments of the present inventionillustrated with reference to drawings. In particular, the detailedoperation of the processor 1010 may refer to the former contentsdescribed with reference to FIG. 1 to FIG. 9.

The memory 1020 is connected with the processor 1010 and stores anoperating system, applications, program codes, data, and the like. TheRF module 1030 is connected with the processor 1010 and then performs afunction of converting a baseband signal to a radio signal or a functionof converting a radio signal to a baseband signal. To this end, the RFmodule 1030 performs an analog conversion, amplification, a filtering,and a frequency up conversion, or performs processes inverse to theformer processes. The display module 1040 is connected with theprocessor 1010 and displays various kinds of informations. And, thedisplay module 1040 can be implemented using such a well-known componentas an LCD (liquid crystal display), an LED (light emitting diode), anOLED (organic light emitting diode) display and the like, by which thepresent invention may be non-limited. The user interface module 1050 isconnected with the processor 1010 and can be configured in a manner ofbeing combined with such a well-known user interface as a keypad, atouchscreen and the like.

The above-described embodiments correspond to combinations of elementsand features of the present invention in prescribed forms. And, therespective elements or features may be considered as selective unlessthey are explicitly mentioned. Each of the elements or features can beimplemented in a form failing to be combined with other elements orfeatures. Moreover, it is able to implement an embodiment of the presentinvention by combining elements and/or features together in part. Asequence of operations explained for each embodiment of the presentinvention can be modified. Some configurations or features of oneembodiment can be included in another embodiment or can be substitutedfor corresponding configurations or features of another embodiment. And,it is apparently understandable that an embodiment is configured bycombining claims failing to have relation of explicit citation in theappended claims together or can be included as new claims by amendmentafter filing an application.

In this disclosure, a specific operation explained as performed by aneNode B may be performed by an upper node of the eNode B in some cases.In particular, in a network constructed with a plurality of networknodes including an eNode B, it is apparent that various operationsperformed for communication with a user equipment can be performed by aneNode B or other networks except the eNode B. ‘eNode B (eNB)’ may besubstituted with such a terminology as a fixed station, a Node B, a basestation (BS), an access point (AP) and the like.

Embodiments of the present invention can be implemented using variousmeans. For instance, embodiments of the present invention can beimplemented using hardware, firmware, software and/or any combinationsthereof. In the implementation by hardware, a method according to eachembodiment of the present invention can be implemented by at least oneselected from the group consisting of ASICs (application specificintegrated circuits), DSPs (digital signal processors), DSPDs (digitalsignal processing devices), PLDs (programmable logic devices), FPGAs(field programmable gate arrays), processor, controller,microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, a methodaccording to each embodiment of the present invention can be implementedby modules, procedures, and/or functions for performing theabove-explained functions or operations. Software code is stored in amemory unit and is then drivable by a processor. The memory unit isprovided within or outside the processor to exchange data with theprocessor through the various means known in public.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

While the method for controlling uplink transmission power in a wirelesscommunication system and the apparatus therefor have been described onthe basis of 3GPP LTE, the present invention is applicable to variouswireless communication systems other than 3GPP LTE.

The invention claimed is:
 1. A method for transmitting, by a userequipment (UE), a sounding reference signal (SRS) to a base station in atime division duplex (TDD) communication system, the method comprising:configuring a first subframe set and a second subframe set based on aRRC (Radio Resource Control) signaling; determining a transmission powerof the SRS based on at least P_(CMAX,c)(i), P_(SRS-OFFSET,c)(m),M_(SRS,c), and f_(c)(i) for the first subframe set, and P_(CMAX,c)(i),P_(SRS-OFFSET,c)(m), M_(SRS,c), and f_(c) ⁽⁰⁾(i) for the second subframeset, wherein P_(CMAX,c)(i) is a configured UE transmit power in subframe‘i’, P_(SRS-OFFSET,c)(m) is a parameter configured for ‘m=0 or 1’,M_(SRS,c) is a bandwidth of the SRS transmission, f_(c)(i) is a currentPhysical Uplink Shared Channel (PUSCH) power control adjustment statefor serving cell ‘c’ in subframe ‘i’ belonging to the first subframeset, and f_(c) ⁽⁰⁾(i) is a current PUSCH power control adjustment statefor serving cell ‘c’ in subframe ‘i’ belonging to the second subframeset, and wherein f_(c)(i) is separately accumulated from a value of aprevious subframe belonging to the first subframe set while f_(c) ⁽⁰⁾(i)is separately accumulated from a value of a previous subframe belongingto the second subframe set; and transmitting the SRS using thedetermined transmission power of the SRS to the base station.
 2. Themethod according to claim 1, wherein each of the first subframe set andthe second subframe set include at least one of an uplink subframe and aspecial subframe.
 3. The method according to claim 1, furthercomprising: receiving configuration information about the first subframeset and the second subframe set from the base station.
 4. A method forreceiving, by a base station, a sounding reference signal (SRS) from auser equipment (UE) in a time division duplex (TDD) communicationsystem, the method comprising: configuring a first subframe set and asecond subframe set through a higher layer; and receiving the SRS fromthe UE on a specific subframe, wherein a transmission power of the SRSis determined by the UE based on at least P_(CMAX,c)(i), P_(SRS) _(_)_(OFFSET,c)(m), M_(SRS,c), and f_(c)(i) for the first subframe set, andP_(CMAX,c)(i), P_(SRS) _(_) _(OFFSET,c)(m), M_(SRS,c),and f_(c) ⁽⁰⁾(i)for the second subframe set, wherein P_(CMAX,c)(i) is a configured UEtransmit power in subframe ‘i’, P_(SRS) _(_) _(OFFSET,c)(m) is aparameter configured for ‘m=0 or 1’, M_(SRS,c) is a bandwidth of the SRStransmission, f_(c)(i) is a current Physical Uplink Shared Channel(PUSCH) power control adjustment state for serving cell ‘c’ in subframe‘i’ belonging to the first subframe set, and f_(c) ⁽⁰⁾(i) is a currentPUSCH power control adjustment state for serving cell ‘c’ in subframe‘i’ belonging to the second subframe set, and wherein f_(c)(i) isseparately accumulated from a value of a previous subframe belonging tothe first subframe set while f_(c) ⁽⁰⁾(i) is separately accumulated froma value of a previous subframe belonging to the second subframe set. 5.The method according to claim 4, wherein each of the first subframe setand the second subframe set include at least one of an uplink subframeand a special subframe.
 6. The method according to claim 4, furthercomprising: transmitting configuration information about the firstsubframe set and the second subframe set to the UE.